(a+b)(a-b)

(a+b)(a-b)

this would solve out to $${{\mathtt{a}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{ab}}{\mathtt{\,\small\textbf+\,}}{\mathtt{ab}}{\mathtt{\,-\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{b}}$$ 

so... the $${\mathtt{ab}}$$(s) will cancel out and you will end with

$${{\mathtt{a}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{b}}$$ (but it'd be 2b not 2 + b)

The answer above is not correct. 

(a - b)(a + b)

= $${{\mathtt{a}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{{\mathtt{b}}}^{{\mathtt{2}}}$$        ✒